Jan. 12

To Do Today

• Turn in HW Sheet

• Go over answers

• Lecture Note Slides:

• Hand back graded quizzes

Relating mass (grams) to Number of atoms

• Using “The Mole”

History of the term “mole”

• Mole is the English version of the German word "Mol" which is short for Molekulargewicht, the "molecular weight.“

• There are claims that it originated as a latin term meaning Mass.

• Started being used around 1900• Used in textbooks by 1950s

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• Q: What does Avogadro put in his hot chocolate?

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•A: Marsh-mole-ows!

Q: What did the generous mole say when his friends crashed his party?

A: The mole the merrier!

Definition of “mole”

• Amount of a substance that contains as many particles as there are atoms in exactly 12 g of carbon-12.

• This Amount is 6.02 x 1023

• It is a “counting unit” just as 1 dozen = 12 of anything.

• 1 mole = 6.02 x 1023 particles

– Chemistry involves vast numbers of atoms.

– we need a convenient unit used for counting atoms.

– (it takes about 500,000 trillion million carbon atoms to equal just one gram.)

– The unit used in Chemistry is the “MOLE”

The Mole Info

• The mole, a fundamental SI unit for "amount of substance," is defined precisely as the number of carbon atoms in 12.01 g of carbon.

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The Mole Info• It is here that the value of

Avogadro's number becomes clear: as noted, carbon has an average atomic mass of 12.01 amu, and multiplication of the average atomic mass by Avogadro's number yields a figure in grams equal to the value of the average atomic mass in atomic mass units. THEREFORE……

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• The mass of 1 mole of any element is equal to its atomic mass expressed in grams

Atomic masses can be found in the periodic table.

– Example:

• C = 12.01 amu

• 1 mol C = 12.011 g C

– Example:

• He = 4 amu

• 1 mol He = 4 g He

– Example:

• N = 14 amu

• 1 mol N = 14 g N

Molar Mass

• The mass of one mole of a substance is called the molar mass of that substance.

• Molar mass is written in g/mol

Molar Mass

• The molar mass of an element is equal to the atomic mass of the element.

• Molar Mass of lithium is

• 6.94 g/mol

• Molar Mass of mercury is

• 200.59 g/mol

Relating grams to # of atoms

• The molar mass of an element contains one mole of atoms.

• In other words, 1 mole of an element contains 6.02 x 1023 atoms of the element

• 1 mole He = 4 grams He = 6.02 x 1023

atoms of He

What is the mass (in grams) of 3.50 mol of copper, Cu?

• Given: 3.50 mol of Cu• Convert between grams and moles using

molar mass• moles of Cu x (g Cu) = grams Cu

moles Cu

3.50 mol Cu x __________ = 222 g Cu63.55 g Cu1 mol Cu

3.50 mol Cu x __________ = 222 g Cu63.55 g Cu1 mol Cu

3 sig digits

What is the mass in grams of 2.25 mol of Fe?

2.25 mol Fe x __________ = 126 g Cu55.85 g Fe

1 mol Fe

3 sig digits

Conversions between grams, moles and # of atoms or

molecules

grams moles# of atoms or molecules

molar m

ass

6.02 x 1023

P 219

• Monatomic ions

• Binary ionic compounds

• Stock system for elements in d block

• Polyatomic ions

• Molecular compounds

P 237

• Formula mass

• Molar mass

• Percentage composition

• Calculation of empirical formulas

• Calculation of molecular formulas

Review equations and reactions

• Balancing equations

• P 268 – 9 molar ratios

• Types of reactions

• Predicting products

Stoichiometry

• Ch 9

Gases

• Gas law